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Auto merge of rust-lang#125958 - BoxyUwU:remove_const_ty, r=lcnr
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Remove the `ty` field from type system `Const`s

Part of the work on `adt_const_params`/`generic_const_param_types`/`min_generic_const_exprs`/generally making the compiler nicer. cc rust-lang/project-const-generics#44

Please review commit-by-commit otherwise I wasted a lot of time not just squashing this into a giant mess (and also it'll be SO much nicer because theres a lot of fluff changes mixed in with other more careful changes if looking via File Changes

---

Why do this?
- The `ty` field keeps causing ICEs and weird behaviour due to it either being treated as "part of the const" or it being forgotten about leading to ICEs.
- As we move forward with `adt_const_params` and a potential `min_generic_const_exprs` it's going to become more complex to actually lower the correct `Ty<'tcx>`
- It muddles the idea behind how we check `Const` arguments have the correct type. By having the `ty` field it may seem like we ought to be relating it when we relate two types, or that its generally important information about the `Const`.
- Brings the compiler more in line with `a-mir-formality` as that also tracks the type of type system `Const`s via `ConstArgHasType` bounds in the env instead of on the `Const` itself.
- A lot of stuff is a lot nicer when you dont have to pass around the type of a const lol. Everywhere we construct `Const` is now significantly nicer 😅

See rust-lang#125671's description for some more information about the `ty` field

---

General summary of changes in this PR:

- Add `Ty` to `ConstKind::Value` as otherwise there is no way to implement `ConstArgHasType` to ensure that const arguments are correctly typed for the parameter when we stop creating anon consts for all const args. It's also just incredibly difficult/annoying to thread the correct `Ty` around to a bunch of ctfe functions otherwise.
-  Fully implement `ConstArgHasType` in both the old and new solver. Since it now has no reliance on the `ty` field it serves its originally intended purpose of being able to act as a double check that trait vs impls have correctly typed const parameters. It also will now be able to be responsible for checking types of const arguments to parameters under `min_generic_const_exprs`.
- Add `Ty` to `mir::Const::Ty`. I dont have a great understanding of why mir constants are setup like this to be honest. Regardless they need to be able to determine the type of the const and the easiest way to make this happen was to simply store the `Ty` along side the `ty::Const`. Maybe we can do better here in the future but I'd have to spend way more time looking at everywhere we use `mir::Const`.
- rustdoc has its own `Const` which also has a `ty` field. It was relatively easy to remove this.

---

r? `@lcnr` `@compiler-errors`
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bors committed Jun 5, 2024
2 parents db8aca4 + 2a0cd39 commit 3878c0d
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Showing 149 changed files with 1,162 additions and 1,228 deletions.
4 changes: 2 additions & 2 deletions compiler/rustc_borrowck/src/type_check/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -346,7 +346,7 @@ impl<'a, 'b, 'tcx> Visitor<'tcx> for TypeVerifier<'a, 'b, 'tcx> {
} else {
let tcx = self.tcx();
let maybe_uneval = match constant.const_ {
Const::Ty(ct) => match ct.kind() {
Const::Ty(_, ct) => match ct.kind() {
ty::ConstKind::Unevaluated(_) => {
bug!("should not encounter unevaluated Const::Ty here, got {:?}", ct)
}
Expand Down Expand Up @@ -1856,7 +1856,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {

if let Operand::Constant(constant) = op {
let maybe_uneval = match constant.const_ {
Const::Val(..) | Const::Ty(_) => None,
Const::Val(..) | Const::Ty(_, _) => None,
Const::Unevaluated(uv, _) => Some(uv),
};

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4 changes: 2 additions & 2 deletions compiler/rustc_borrowck/src/type_check/relate_tys.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -193,7 +193,7 @@ impl<'me, 'bccx, 'tcx> NllTypeRelating<'me, 'bccx, 'tcx> {
types: &mut |_bound_ty: ty::BoundTy| {
unreachable!("we only replace regions in nll_relate, not types")
},
consts: &mut |_bound_var: ty::BoundVar, _ty| {
consts: &mut |_bound_var: ty::BoundVar| {
unreachable!("we only replace regions in nll_relate, not consts")
},
};
Expand Down Expand Up @@ -231,7 +231,7 @@ impl<'me, 'bccx, 'tcx> NllTypeRelating<'me, 'bccx, 'tcx> {
types: &mut |_bound_ty: ty::BoundTy| {
unreachable!("we only replace regions in nll_relate, not types")
},
consts: &mut |_bound_var: ty::BoundVar, _ty| {
consts: &mut |_bound_var: ty::BoundVar| {
unreachable!("we only replace regions in nll_relate, not consts")
},
};
Expand Down
1 change: 1 addition & 0 deletions compiler/rustc_codegen_cranelift/src/intrinsics/simd.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -133,6 +133,7 @@ pub(super) fn codegen_simd_intrinsic_call<'tcx>(
.expect_const()
.eval(fx.tcx, ty::ParamEnv::reveal_all(), span)
.unwrap()
.1
.unwrap_branch();

assert_eq!(x.layout(), y.layout());
Expand Down
1 change: 1 addition & 0 deletions compiler/rustc_codegen_llvm/src/intrinsic.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -1201,6 +1201,7 @@ fn generic_simd_intrinsic<'ll, 'tcx>(
.expect_const()
.eval(tcx, ty::ParamEnv::reveal_all(), span)
.unwrap()
.1
.unwrap_branch();
let n = idx.len() as u64;

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71 changes: 38 additions & 33 deletions compiler/rustc_codegen_ssa/src/debuginfo/type_names.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -693,41 +693,46 @@ fn push_const_param<'tcx>(tcx: TyCtxt<'tcx>, ct: ty::Const<'tcx>, output: &mut S
ty::ConstKind::Param(param) => {
write!(output, "{}", param.name)
}
_ => match ct.ty().kind() {
ty::Int(ity) => {
let bits = ct.eval_bits(tcx, ty::ParamEnv::reveal_all());
let val = Integer::from_int_ty(&tcx, *ity).size().sign_extend(bits) as i128;
write!(output, "{val}")
}
ty::Uint(_) => {
let val = ct.eval_bits(tcx, ty::ParamEnv::reveal_all());
write!(output, "{val}")
}
ty::Bool => {
let val = ct.try_eval_bool(tcx, ty::ParamEnv::reveal_all()).unwrap();
write!(output, "{val}")
}
_ => {
// If we cannot evaluate the constant to a known type, we fall back
// to emitting a stable hash value of the constant. This isn't very pretty
// but we get a deterministic, virtually unique value for the constant.
//
// Let's only emit 64 bits of the hash value. That should be plenty for
// avoiding collisions and will make the emitted type names shorter.
let hash_short = tcx.with_stable_hashing_context(|mut hcx| {
let mut hasher = StableHasher::new();
let ct = ct.eval(tcx, ty::ParamEnv::reveal_all(), DUMMY_SP).unwrap();
hcx.while_hashing_spans(false, |hcx| ct.hash_stable(hcx, &mut hasher));
hasher.finish::<Hash64>()
});

if cpp_like_debuginfo(tcx) {
write!(output, "CONST${hash_short:x}")
} else {
write!(output, "{{CONST#{hash_short:x}}}")
ty::ConstKind::Value(ty, _) => {
match ty.kind() {
ty::Int(ity) => {
// FIXME: directly extract the bits from a valtree instead of evaluating an
// alreay evaluated `Const` in order to get the bits.
let bits = ct.eval_bits(tcx, ty::ParamEnv::reveal_all());
let val = Integer::from_int_ty(&tcx, *ity).size().sign_extend(bits) as i128;
write!(output, "{val}")
}
ty::Uint(_) => {
let val = ct.eval_bits(tcx, ty::ParamEnv::reveal_all());
write!(output, "{val}")
}
ty::Bool => {
let val = ct.try_eval_bool(tcx, ty::ParamEnv::reveal_all()).unwrap();
write!(output, "{val}")
}
_ => {
// If we cannot evaluate the constant to a known type, we fall back
// to emitting a stable hash value of the constant. This isn't very pretty
// but we get a deterministic, virtually unique value for the constant.
//
// Let's only emit 64 bits of the hash value. That should be plenty for
// avoiding collisions and will make the emitted type names shorter.
let hash_short = tcx.with_stable_hashing_context(|mut hcx| {
let mut hasher = StableHasher::new();
let ct = ct.eval(tcx, ty::ParamEnv::reveal_all(), DUMMY_SP).unwrap();
hcx.while_hashing_spans(false, |hcx| ct.hash_stable(hcx, &mut hasher));
hasher.finish::<Hash64>()
});

if cpp_like_debuginfo(tcx) {
write!(output, "CONST${hash_short:x}")
} else {
write!(output, "{{CONST#{hash_short:x}}}")
}
}
}
},
}
_ => bug!("Invalid `Const` during codegen: {:?}", ct),
}
.unwrap();
}
Expand Down
4 changes: 2 additions & 2 deletions compiler/rustc_codegen_ssa/src/mir/constant.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -40,10 +40,10 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
) -> Result<Option<ty::ValTree<'tcx>>, ErrorHandled> {
let uv = match self.monomorphize(constant.const_) {
mir::Const::Unevaluated(uv, _) => uv.shrink(),
mir::Const::Ty(c) => match c.kind() {
mir::Const::Ty(_, c) => match c.kind() {
// A constant that came from a const generic but was then used as an argument to old-style
// simd_shuffle (passing as argument instead of as a generic param).
rustc_type_ir::ConstKind::Value(valtree) => return Ok(Some(valtree)),
rustc_type_ir::ConstKind::Value(_, valtree) => return Ok(Some(valtree)),
other => span_bug!(constant.span, "{other:#?}"),
},
// We should never encounter `Const::Val` unless MIR opts (like const prop) evaluate
Expand Down
6 changes: 3 additions & 3 deletions compiler/rustc_const_eval/src/check_consts/qualifs.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -357,15 +357,15 @@ where

// Check the qualifs of the value of `const` items.
let uneval = match constant.const_ {
Const::Ty(ct)
Const::Ty(_, ct)
if matches!(
ct.kind(),
ty::ConstKind::Param(_) | ty::ConstKind::Error(_) | ty::ConstKind::Value(_)
ty::ConstKind::Param(_) | ty::ConstKind::Error(_) | ty::ConstKind::Value(_, _)
) =>
{
None
}
Const::Ty(c) => {
Const::Ty(_, c) => {
bug!("expected ConstKind::Param or ConstKind::Value here, found {:?}", c)
}
Const::Unevaluated(uv, _) => Some(uv),
Expand Down
3 changes: 0 additions & 3 deletions compiler/rustc_hir_analysis/src/check/compare_impl_item.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -2198,9 +2198,6 @@ fn param_env_with_gat_bounds<'tcx>(
tcx,
ty::INNERMOST,
ty::BoundVar::from_usize(bound_vars.len() - 1),
tcx.type_of(param.def_id)
.no_bound_vars()
.expect("const parameter types cannot be generic"),
)
.into()
}
Expand Down
12 changes: 2 additions & 10 deletions compiler/rustc_hir_analysis/src/collect.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -386,16 +386,8 @@ impl<'tcx> HirTyLowerer<'tcx> for ItemCtxt<'tcx> {
Ty::new_error_with_message(self.tcx(), span, "bad placeholder type")
}

fn ct_infer(&self, ty: Ty<'tcx>, _: Option<&ty::GenericParamDef>, span: Span) -> Const<'tcx> {
let ty = self.tcx.fold_regions(ty, |r, _| match *r {
rustc_type_ir::RegionKind::ReStatic => r,

// This is never reached in practice. If it ever is reached,
// `ReErased` should be changed to `ReStatic`, and any other region
// left alone.
r => bug!("unexpected region: {r:?}"),
});
ty::Const::new_error_with_message(self.tcx(), ty, span, "bad placeholder constant")
fn ct_infer(&self, _: Option<&ty::GenericParamDef>, span: Span) -> Const<'tcx> {
ty::Const::new_error_with_message(self.tcx(), span, "bad placeholder constant")
}

fn probe_ty_param_bounds(
Expand Down
2 changes: 1 addition & 1 deletion compiler/rustc_hir_analysis/src/collect/predicates_of.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -197,7 +197,7 @@ fn gather_explicit_predicates_of(tcx: TyCtxt<'_>, def_id: LocalDefId) -> ty::Gen
.type_of(param.def_id.to_def_id())
.no_bound_vars()
.expect("const parameters cannot be generic");
let ct = icx.lowerer().lower_const_param(param.hir_id, ct_ty);
let ct = icx.lowerer().lower_const_param(param.hir_id);
predicates
.insert((ty::ClauseKind::ConstArgHasType(ct, ct_ty).upcast(tcx), param.span));
}
Expand Down
6 changes: 1 addition & 5 deletions compiler/rustc_hir_analysis/src/hir_ty_lowering/bounds.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -366,11 +366,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
},
)
});
let ty = tcx
.type_of(param.def_id)
.no_bound_vars()
.expect("ct params cannot have early bound vars");
ty::Const::new_error(tcx, guar, ty).into()
ty::Const::new_error(tcx, guar).into()
}
};
num_bound_vars += 1;
Expand Down
56 changes: 24 additions & 32 deletions compiler/rustc_hir_analysis/src/hir_ty_lowering/mod.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -103,12 +103,7 @@ pub trait HirTyLowerer<'tcx> {
fn ty_infer(&self, param: Option<&ty::GenericParamDef>, span: Span) -> Ty<'tcx>;

/// Returns the const to use when a const is omitted.
fn ct_infer(
&self,
ty: Ty<'tcx>,
param: Option<&ty::GenericParamDef>,
span: Span,
) -> Const<'tcx>;
fn ct_infer(&self, param: Option<&ty::GenericParamDef>, span: Span) -> Const<'tcx>;

/// Probe bounds in scope where the bounded type coincides with the given type parameter.
///
Expand Down Expand Up @@ -438,15 +433,15 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {

fn provided_kind(
&mut self,
preceding_args: &[ty::GenericArg<'tcx>],
_preceding_args: &[ty::GenericArg<'tcx>],
param: &ty::GenericParamDef,
arg: &GenericArg<'tcx>,
) -> ty::GenericArg<'tcx> {
let tcx = self.lowerer.tcx();

if let Err(incorrect) = self.incorrect_args {
if incorrect.invalid_args.contains(&(param.index as usize)) {
return param.to_error(tcx, preceding_args);
return param.to_error(tcx);
}
}

Expand Down Expand Up @@ -491,16 +486,11 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
ty::Const::from_anon_const(tcx, did).into()
}
(&GenericParamDefKind::Const { .. }, hir::GenericArg::Infer(inf)) => {
let ty = tcx
.at(self.span)
.type_of(param.def_id)
.no_bound_vars()
.expect("const parameter types cannot be generic");
if self.lowerer.allow_infer() {
self.lowerer.ct_infer(ty, Some(param), inf.span).into()
self.lowerer.ct_infer(Some(param), inf.span).into()
} else {
self.inferred_params.push(inf.span);
ty::Const::new_misc_error(tcx, ty).into()
ty::Const::new_misc_error(tcx).into()
}
}
(kind, arg) => span_bug!(
Expand All @@ -520,7 +510,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {

if let Err(incorrect) = self.incorrect_args {
if incorrect.invalid_args.contains(&(param.index as usize)) {
return param.to_error(tcx, preceding_args);
return param.to_error(tcx);
}
}
match param.kind {
Expand Down Expand Up @@ -568,7 +558,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
.no_bound_vars()
.expect("const parameter types cannot be generic");
if let Err(guar) = ty.error_reported() {
return ty::Const::new_error(tcx, guar, ty).into();
return ty::Const::new_error(tcx, guar).into();
}
// FIXME(effects) see if we should special case effect params here
if !infer_args && has_default {
Expand All @@ -577,10 +567,10 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
.into()
} else {
if infer_args {
self.lowerer.ct_infer(ty, Some(param), self.span).into()
self.lowerer.ct_infer(Some(param), self.span).into()
} else {
// We've already errored above about the mismatch.
ty::Const::new_misc_error(tcx, ty).into()
ty::Const::new_misc_error(tcx).into()
}
}
}
Expand Down Expand Up @@ -1930,7 +1920,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
///
/// Early-bound const parameters get lowered to [`ty::ConstKind::Param`]
/// and late-bound ones to [`ty::ConstKind::Bound`].
pub(crate) fn lower_const_param(&self, hir_id: HirId, param_ty: Ty<'tcx>) -> Const<'tcx> {
pub(crate) fn lower_const_param(&self, hir_id: HirId) -> Const<'tcx> {
let tcx = self.tcx();
match tcx.named_bound_var(hir_id) {
Some(rbv::ResolvedArg::EarlyBound(def_id)) => {
Expand All @@ -1940,12 +1930,12 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
let generics = tcx.generics_of(item_def_id);
let index = generics.param_def_id_to_index[&def_id];
let name = tcx.item_name(def_id);
ty::Const::new_param(tcx, ty::ParamConst::new(index, name), param_ty)
ty::Const::new_param(tcx, ty::ParamConst::new(index, name))
}
Some(rbv::ResolvedArg::LateBound(debruijn, index, _)) => {
ty::Const::new_bound(tcx, debruijn, ty::BoundVar::from_u32(index), param_ty)
ty::Const::new_bound(tcx, debruijn, ty::BoundVar::from_u32(index))
}
Some(rbv::ResolvedArg::Error(guar)) => ty::Const::new_error(tcx, guar, param_ty),
Some(rbv::ResolvedArg::Error(guar)) => ty::Const::new_error(tcx, guar),
arg => bug!("unexpected bound var resolution for {:?}: {arg:?}", hir_id),
}
}
Expand Down Expand Up @@ -2161,7 +2151,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
}
hir::TyKind::Array(ty, length) => {
let length = match length {
hir::ArrayLen::Infer(inf) => self.ct_infer(tcx.types.usize, None, inf.span),
hir::ArrayLen::Infer(inf) => self.ct_infer(None, inf.span),
hir::ArrayLen::Body(constant) => {
ty::Const::from_anon_const(tcx, constant.def_id)
}
Expand Down Expand Up @@ -2192,17 +2182,18 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
}
_ => (expr, None),
};
let c = match &expr.kind {
let (c, c_ty) = match &expr.kind {
hir::ExprKind::Lit(lit) => {
let lit_input =
LitToConstInput { lit: &lit.node, ty, neg: neg.is_some() };
match tcx.lit_to_const(lit_input) {
let ct = match tcx.lit_to_const(lit_input) {
Ok(c) => c,
Err(LitToConstError::Reported(err)) => {
ty::Const::new_error(tcx, err, ty)
ty::Const::new_error(tcx, err)
}
Err(LitToConstError::TypeError) => todo!(),
}
};
(ct, ty)
}

hir::ExprKind::Path(hir::QPath::Resolved(
Expand All @@ -2220,19 +2211,20 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
.type_of(def_id)
.no_bound_vars()
.expect("const parameter types cannot be generic");
self.lower_const_param(expr.hir_id, ty)
let ct = self.lower_const_param(expr.hir_id);
(ct, ty)
}

_ => {
let err = tcx
.dcx()
.emit_err(crate::errors::NonConstRange { span: expr.span });
ty::Const::new_error(tcx, err, ty)
(ty::Const::new_error(tcx, err), Ty::new_error(tcx, err))
}
};
self.record_ty(expr.hir_id, c.ty(), expr.span);
self.record_ty(expr.hir_id, c_ty, expr.span);
if let Some((id, span)) = neg {
self.record_ty(id, c.ty(), span);
self.record_ty(id, c_ty, span);
}
c
};
Expand Down
5 changes: 2 additions & 3 deletions compiler/rustc_hir_analysis/src/hir_ty_lowering/object_safety.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -141,9 +141,8 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
// `trait_object_dummy_self`, so check for that.
let references_self = match pred.skip_binder().term.unpack() {
ty::TermKind::Ty(ty) => ty.walk().any(|arg| arg == dummy_self.into()),
ty::TermKind::Const(c) => {
c.ty().walk().any(|arg| arg == dummy_self.into())
}
// FIXME(associated_const_equality): We should walk the const instead of not doing anything
ty::TermKind::Const(_) => false,
};

// If the projection output contains `Self`, force the user to
Expand Down
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